U.S. patent application number 10/874364 was filed with the patent office on 2005-01-13 for method and apparatus for applying an ink image to a receiving material.
Invention is credited to De Grijs, Eduard T. H., Stoot, Andreas C..
Application Number | 20050005800 10/874364 |
Document ID | / |
Family ID | 33560817 |
Filed Date | 2005-01-13 |
United States Patent
Application |
20050005800 |
Kind Code |
A1 |
Stoot, Andreas C. ; et
al. |
January 13, 2005 |
Method and apparatus for applying an ink image to a receiving
material
Abstract
An apparatus for applying an ink image to a receiving material
adapted to be advanced in a specific direction which includes an
ink application system for applying an ink image to a strip of
receiving material, which strip extends in a direction transverse
to the direction of advance of the receiving material, the ink
application means being movable over the strip of receiving
material, a carrier device for maintaining the strip in a
predetermined position with respect to the ink application system,
which carrier device includes a carrier plate for carrying the
strip, said carrier plate having recesses and said carrier plate
being provided with holes, a vacuum device for sucking away air via
said holes from the space between the carrier plate and a strip of
receiving material lying on the carrier plate, and correction means
for correcting local variations in the distance between the
receiving material and the ink application mean.
Inventors: |
Stoot, Andreas C.; (Venlo,
NL) ; De Grijs, Eduard T. H.; (Venlo, NL) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
33560817 |
Appl. No.: |
10/874364 |
Filed: |
June 24, 2004 |
Current U.S.
Class: |
101/483 ;
427/282; 427/294 |
Current CPC
Class: |
B41J 11/0085 20130101;
B41J 11/20 20130101; B41J 11/06 20130101; B41J 25/308 20130101 |
Class at
Publication: |
101/483 ;
427/294; 427/282 |
International
Class: |
B41M 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 27, 2003 |
EP |
03077004.4 |
Claims
What is clamed is:
1. An apparatus for applying an ink image to a receiving material
adapted to be advanced in a desired direction which comprises: ink
application means for applying an ink image to a strip of receiving
material, said strip extending in a direction transverse to the
direction of advance of the receiving material, wherein the ink
application means is movable over the strip of receiving material,
carrier means for maintaining said strip in a predetermined
position with respect to the ink application means, said carrier
means including a carrier plate for carrying said strip, said
carrier plate having recesses and said carrier plate being provided
with holes, vacuum means for sucking away air via said holes from
the space between the carrier plate and a strip of receiving
material lying on the carrier plate, and correction means for
correcting local variations in the distance between the receiving
material and the ink application means.
2. The apparatus as claimed in claim 1, wherein the correction
means comprise timing means for adjusting the moment the ink
released by the ink application means.
3. The apparatus as claimed in claim 2, wherein the timing means
are arranged for advancing the moment of ink release when the ink
application means approaches a downward slope of a recess, and for
delaying the moment of ink release when the ink application means
approaches an upward slope of a recess.
4. The apparatus as claimed in claim 2, wherein the ink application
means are arranged for moving with uniform velocity over the
carrier plate.
5. The apparatus as claimed claim 1, wherein the correction means
comprises speed adjustment means for adjusting the relative
velocity between the ink application means and the carrier
plate.
6. The apparatus as claimed in claim 5, wherein the speed
adjustment means are arranged for reducing the relative velocity
when the ink application means approaches a downward slope of a
recess, and for increasing the relative velocity when the ink
application means approaches an upward slope of a recess.
7. The apparatus as claimed in claim 5, wherein the speed
adjustment means comprises a translation means for moving the
carrier plate in a direction substantially parallel to the
direction of the strip of receiving material.
8. The apparatus as claimed in claim 7, wherein the translation
means is arranged for a reciprocating movement of the carrier
plate.
9. The apparatus as claimed in claim 5, wherein the speed
adjustment means comprises means for adjusting the velocity of the
ink application means.
10. The apparatus as claimed in claim 1, wherein the correction
means comprises adjustment means for adjusting the distance between
the ink application means and the carrier plate.
11. The apparatus as claimed in claim 10, wherein the adjustment
means comprise first movement means for moving the carrier plate in
a direction for adjusting the distance between the ink application
means and the carrier plate.
12. The apparatus as claimed in claim 11, wherein the adjustment
means comprises a second movement means for moving the ink
application means in a direction for adjusting the distance between
the ink application means and the carrier plate.
13. The apparatus as claimed in claim 1, wherein the correction
means are controllable by an undulatory electronic signal, wherein
the leading and tailing edges of the undulatory signal correspond
with downward and upward slopes of the recesses.
14. The apparatus as claimed in claim 1, wherein the apparatus
further comprises controlling means for controlling the correction
means depending on at least one of a plurality of characteristics
including receiving material characteristics, ink characteristics,
ink image characteristics, print mode, carrier plate
characteristics, distance between the ink application means and the
carrier plate, and the velocity of the ink application means with
respect to the carrier plate.
15. The apparatus as claimed in claim 14, wherein the receiving
material characteristics includes at least one of the grade, the
type, the thickness, the moisture content, the weight or substance
per unit area, and the sizing.
16. The apparatus as claimed in claim 14, wherein the ink
characteristics include at least one of the viscosity and wetting
characteristics of the ink.
17. The apparatus as claimed in claim 14, wherein the ink image
characteristics include at least one of the characteristics
selected from the group comprising the area fraction covered by ink
and pixel density.
18. The apparatus as claimed in claim 14, wherein the print mode
comprises at least one of the last mode, the normal mode, and the
best mode.
19. The apparatus as claimed in claim 14, wherein the carrier plate
characteristics comprise at least one of the configuration and/or
profile of the recesses and magnitude of a vacuum pressure
generated by the vacuum means,
20. The apparatus as claimed in claim 19, further comprising
detection means for detecting the positions of the recesses with
respect to a path of the ink application means.
21. The apparatus as claimed in claim 14, wherein the controlling
means includes input means for inputting at least one of said
characteristics.
22. A method for applying an ink image to a receiving material
using an apparatus adapted to advance the receiving material in a
desired direction which comprises: placing a strip of receiving
material on a carrier means in a predetermined position with
respect to an ink application means, said carrier means comprising
a carrier plate for carrying said strip, said carrier plate having
recesses and said carrier plate being provided with holes,
maintaining the strip of receiving material on the carrier means by
sucking away air via said holes from the space between the carrier
plate and the strip of receiving material lying on the carrier
plate using vacuum means, applying an ink image to a strip of
receiving material using an ink application means, said strip
extending in a direction transverse to the direction of advance of
the receiving material, and correcting local variations in the
distance between the receiving material and the ink application
means using correction means.
23. The method as claimed in claim 22, wherein the correction means
comprises timing means for adjusting the moment the ink is
released.
24. The method as claimed in claim 22, wherein the correction means
comprises speed adjustment means for adjusting the relative
velocity between the application of ink and the carrier plate.
25. The method as claimed in claim 22, wherein the correction means
comprises adjustment means for adjusting the distance between the
ink application and the carrier plate.
26. The method as claimed in claim 22, wherein the correction means
are controlled by an undulatory electronic signal, wherein the
leading and tailing edges of the undulatory signal correspond with
downward and upward slopes of the recesses.
27. The method as claimed in claim 22, wherein the correction means
are controlled by controlling means for controlling the correction
means depending on at least one of a plurality of characteristics
including receiving material characteristics, ink characteristics,
ink image characteristics, print mode, carrier plate
characteristics, distance between the ink application means and the
carrier plate, and the velocity of the ink application means with
respect to the carrier plate.
28. An apparatus for applying an ink image to a receiving material
which comprises: ink application means for applying an ink image to
a strip of receiving material, carrier means for maintaining said
strip in a predetermined position with respect to the ink
application means, said carrier means including a carrier plate,
containing recesses, whereby the receiving material sags into said
recesses causing a variation in distance between the ink
application means and the receiving material, and correction means
for correcting said variations in the distance between the ink
application means and the receiving material.
29. The apparatus of claim 28 wherein the correction means is a
timing means for adjusting the moment of ink release by the
printhead.
30. The apparatus of claim 28 wherein the correction means is a
speed adjustment means for adjusting the relative velocity of the
ink application means with respect to the carrier plate.
31. The apparatus of claim 28 wherein the correction means is a
means for adjusting the distance between the ink application means
and the carrier plate.
Description
[0001] This non-provisional application claims priority under 35
U.S.C. .sctn. 119(a) on Patent Application No. 03077004.4 filed in
Europe on Jun. 27, 2003, which is herein incorporated by
reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to an apparatus for applying
an ink image to a receiving material. More particularly the present
invention relates to copiers or printers, for example, photocopiers
or inkjet printers, wherein the receiving material is retained
against a carrier plate. The present invention further relates to a
method for applying an ink image to a receiving material.
[0003] An apparatus for maintaining a receiving material flat
against a carrier plate during the application of an ink image
thereto is generally known. The carrier plate is, for example,
provided with V-shaped channels, which extend in the direction in
which the receiving material is movable stepwise, over the carrier
plate. Ribs which separate the channels from one another are
provided with suction openings in order to draw bubbles, which are
formed by moisture absorption in the receiving material, into the
channels by vacuum pressure, in order to prevent the bubbles from
coming into contact there with ink application means which are
flatly movable over the carrier plate.
[0004] The receiving material is pulled against the carrier plate
with considerable force so that it is possible to ensure with a
great degree of certainty that parts of the receiving material,
particularly bubbles extending in the direction of the ink
application means, remain out of contact with the ink application
means.
[0005] A disadvantage of the known apparatus is that the ink images
on some receiving materials are distorted due to, for example,
locally occurring line broadening and density variations in
area-fills.
SUMMARY OF THE INVENTION
[0006] An object of the present invention is to eliminate the
disadvantages existing in known apparatus.
[0007] A further object of the present invention is to provide an
apparatus having an improved control over the process of the
application of an ink image onto a receiving material in order to,
at least, reduce the distortions mentioned above.
[0008] From one aspect, the present invention provides an apparatus
for applying an ink image to a receiving material adapted to be
advanced in a direction of advance, comprising:
[0009] ink application means for applying an ink image to a strip
of receiving material, which strip extends in a direction
transverse to the direction of advance of the receiving material,
wherein the ink application means are movable over the strip of
receiving material,
[0010] carrier means for maintaining the strip in a predetermined
position with respect to the ink application means, which carrier
means includes a carrier plate for carrying the strip, said carrier
plate having recesses and provided with holes,
[0011] vacuum means for sucking away air via said holes from the
space between the carrier plate and a strip of receiving material
lying on the carrier plate, and
[0012] correction means for correcting local variations in the
distance between the receiving material and the ink application
means.
[0013] Some receiving materials, particularly slack or compliant
receiving materials, are pulled into the recesses to some extent
due to the vacuum pressure. On the one hand this is advantageous
since it reduces the extent to which bubbles extend in the
direction of the ink application means. On the other hand, the
sagging of the receiving material into the recesses may result in
positioning errors in the ink image.
[0014] For example, in the case a line of equidistant dots is to be
printed onto the receiving material, the ink image of these dots
can be distorted when the line crosses a part of the receiving
material that has sagged into a recess. In the direction of
movement of the ink application means, the distance between the
dots on the receiving material will increase when the ink
application means moves over a downward slope of the sagged
receiving material. This distance will decrease when the ink
application means moves over an upward slope of the sagged
receiving material. Since this distortion of the ink image is
repeated in each strip of receiving material, these distortions add
up to form a pattern in the direction of advance of the receiving
material.
[0015] Moreover, the carrier plate can be provided with a series of
regularly spaced recesses or channels as known in the art. As a
consequence of this, the above-mentioned distortions appear around
the position of each recess, so that these distortions add up to
form a longitudinal wave pattern in a direction perpendicular to
the direction of advance of the receiving material.
[0016] Providing the apparatus for applying an ink image to a
receiving material with a correction system for at least partially
correcting local variations in the distance between the receiving
material and the ink application means has been found to result in
a substantial improvement in the ink image due to a reduction in
the misalignment of the ink dots which make up the ink image.
[0017] In a first embodiment, the correction means comprise timing
means for adjusting the moment of ink release by the ink
application means. Local distance variations cause variations in
flight time of the ink droplets from the ink application means to
the receiving material. Said variations in flight time of the ink
droplets can be compensated for by adjusting the moment of ink
release. For example, when the receiving material has sagged into a
recess, the distance between the receiving material and the ink
application means is locally enlarged and the flight time of the
ink droplet will increase. Advancing the moment of ink release by
the ink application means can compensate for this increased flight
time and can correct the misalignment of the position of the ink
droplet due to the sagging of the receiving material into the
recess.
[0018] In a further development, the timing means are arranged for
advancing the moment of ink release when the ink application means
is near a downward slope of a recess, and for delaying the moment
of ink release when the ink application means is near an upward
slope of a recess. Preferably the advance and delay are defined by
an undulatory electronic signal, wherein the leading and tailing
edges of the undulatory signal correspond to the downward and
upward slopes of the recesses, respectively. The differences in
flight time can thus be corrected using a simple electronic
correction of the signal that controls the moment of ink release by
the ink application means.
[0019] In a further development, the ink application means are
arranged for moving with uniform velocity over the carrier plate.
In this case, and in combination with regularly spaced recesses on
the carrier plate, the undulatory electronic signal is also
regular, and a simple regular electronic wave signal can be
used.
[0020] In a second embodiment, the correction means comprises speed
adjustment means for adjusting the relative velocity between the
ink application means and the carrier plate. In a further
development, the speed adjustment means are arranged for reducing
the relative velocity when the ink application means is near a
downward slope of a recess, and for increasing the relative
velocity when the ink application means is near an upward slope of
a recess. Due to this variation in relative velocity between the
ink application means and the carrier plate, the trajectories of
the ink droplets can be adjusted to compensate for local distance
variations between the ink application means and the receiving
material.
[0021] The adjustment of the relative velocity between the ink
application means and the carrier plate, can be carried out with
the speed adjustment means which comprises a translation system for
moving the carrier plate in a direction substantially parallel to
the direction of the strip of receiving material. In a further
development, the translation means are arranged for a reciprocating
movement of the carrier plate. Such a translation means for moving
the carrier plate has the advantage that no changes have to be made
to the ink application means, and that the known ink application
means can be used in the apparatus of the present invention.
[0022] Alternatively, the speed adjustment means comprises means
for adjusting the velocity of the ink application means. This
adjustment of the velocity of the application means may be defined
by an undulatory electronic signal, wherein the leading and tailing
edges of the undulatory signal correspond to the downward and
upward slopes of the recesses, respectively. The variation of the
velocity can thus be achieved by a simple electronic correction of
a signal for controlling the velocity of the ink application
means.
[0023] The above-mentioned means for adjusting the velocity of the
ink application means and the translation means for moving the
carrier plate in the direction substantially parallel to the
direction of the strip of receiving material, can also be combined.
In this case the required adjustment of the relative velocity
between the ink application means and the carrier plate can be
divided between the means for adjusting the velocity of the ink
application means and the translation means. In this way the amount
of adjustment of each of these means can be reduced. In particular,
the velocity of the translation means for moving the carrier plate
can be reduced.
[0024] A further advantage of the above mentioned first and second
embodiments is that the distance between the carrier plate and the
ink application means is not affected by the correction means. Thus
the risk that the receiving material may come into contact with the
ink application means is as low as in the prior art.
[0025] In a third embodiment the correction means comprises an
adjustment means for locally adjusting the distance between the ink
application means and the carrier plate. In a further development,
this adjustment results in essentially a constant distance between
the ink application means and the receiving material. This
adjustment of the distance may also be defined by an undulatory
electronic signal where the leading and tailing edges of the
undulatory signal correspond with the downward and upward slopes of
the recesses.
[0026] In a further development, the adjustment means comprises
first movement means for moving the carrier plate in a direction
for adjusting the distance between the ink application means and
the carrier plate. The adjustment means may also, or in addition,
comprise a second movement means for moving the ink application
means in a direction for adjusting the distance between the ink
application means and the carrier plate. In an apparatus comprising
first and second movement means, the extent of adjustment can be
divided between these two movement means, thereby reducing the
required amount of adjustment of each of these movement means.
[0027] In a preferred embodiment the apparatus further comprises
controlling means for controlling the correction means depending on
of at least one of the following characteristics, i.e., receiving
material characteristics, ink characteristics, ink image
characteristics, print mode, carrier plate characteristics,
distance between the ink application means and the carrier plate,
and the velocity of the ink application means with respect to the
carrier plate. Using at least one of these characteristics, the
extent to which the receiving material is pulled into the recesses,
can be estimated, derived or determined. The controlling means
controls the correction means for correcting this estimated extent
of sagging of the receiving material into the recesses. The use of
such a controlling means results in a very flexible apparatus,
which can easily adapt to various conditions such as, for example,
various different types of receiving materials.
[0028] In a further development, the controlling means includes
input means for inputting these characteristics. One or more of
these characteristics or values defining the state of these
characteristics may be inputted or modified via the input means
when changing, for example, from one type of receiving material to
another type of receiving material or from one type of printing ink
to another type of printing ink. The values may be numerical
values, but may also include other characters, such as alphanumeric
characters.
[0029] The receiving material characteristics may include at least
one of the following characteristics, including the grade, the
type, the thickness, the moisture content, the weight or substance
per unit area, and the sizing.
[0030] The ink characteristics may include at least one of the
following characteristics, including the viscosity, the water or
solvent content of the ink, and the wetting characteristics of the
ink.
[0031] The ink image characteristics may include at least one of
the following characteristics, including area fraction covered by
ink, pixel density and the like.
[0032] The print mode may be one of a last mode, normal mode, and
best mode. In the last mode, the ink image is printed in one single
move of the ink application means over the strip of receiving
material. In the normal mode, the ink image is printed in a
reciprocating movement of the ink application means over the strip
of receiving material. In the best mode, the ink image is printed
in more than one forward motion or reciprocating motion.
[0033] The carrier plate characteristics may include at least one
of the following characteristics, including configuration of the
recesses, profile of the recesses and magnitude of the vacuum
pressure generated by the vacuum means.
[0034] In a further development, the apparatus includes a detection
means for detecting the positions of the recesses with respect to a
path of the ink application means. The information about the
relative position of the recesses with respect to the path of the
application means can then be transferred to the controlling means.
This information can be used for controlling the correction means
as described above. The detection means can be used for the
calibration or recalibration of the correction means and may, for
example, be used in a start-up phase of the apparatus according to
the present invention for detecting the relative positions of the
recesses with respect to the actual path of the ink application
means.
[0035] From a second aspect, the present invention provides a
method for applying an ink image to a receiving material using an
apparatus adapted to advance the receiving material in a direction
of advance, wherein the method includes the steps of:
[0036] placing a strip of receiving material on a carrier means in
a predetermined position with respect to an ink application means,
which carrier means is a carrier plate for carrying the strip,
wherein the carrier plate contains recesses extending in the
direction substantially parallel to the direction of advance of the
receiving material, and the carrier plate is provided with
holes,
[0037] maintaining the strip of receiving material on the carrier
means by using a vacuum means to draw air via said holes from the
space between the carrier plate and the strip of receiving material
lying on the carrier plate,
[0038] applying an ink image to the strip of receiving material
using the ink application means, which strip extends in the
direction transverse to the direction of advance of the receiving
material, and
[0039] correcting local variations in the distance between the
receiving material and the ink application means using correction
means during the movement of the application means over the strip
of receiving material.
[0040] The correction can be performed by adjusting the moment of
ink released by the ink application means, using timing means as
described above.
[0041] In addition or alternatively, the local variations can also
be corrected by adjusting the relative velocity with which the ink
application means is moved over the carrier plate for applying the
ink image to the strip of receiving material.
[0042] Furthermore, adjusting the distance between the ink
application means and the carrier plate can correct the local
variations.
[0043] In a further development, the local variations in the
distance between the receiving material and the ink application
means are estimated or determined using at least one of many
characteristics including ink characteristics, receiving material
characteristics, ink image characteristics, print mode, carrier
plate characteristics, distance between the ink application means
and the carrier plate, and the velocity of the ink application
means with respect to the carrier plate. Such characteristics may
be inputted into the controlling means for controlling the
correction means.
[0044] Further scope of applicability of the present invention will
become apparent from the detailed description given hereinafter.
However, it should be understood that the detailed description and
specific examples, while indicating preferred embodiments of the
invention, are given by way of illustration only, since various
changes and modifications within the spirit and scope of the
invention will become apparent to those skilled in the art from
this detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0045] The present invention will become more fully understood from
the detailed description given hereinbelow and the accompanying
drawings, which are given by way of illustration only, and thus are
not limitative of the present invention, and wherein:
[0046] FIG. 1 is a top perspective view of a detail of an apparatus
according to the prior art;
[0047] FIG. 2 is a cross-sectional view of a detail of the carrier
means;
[0048] FIGS. 3A, 3B and 3C are schematic representations of
exemplary embodiments according to the present invention;
[0049] FIG. 4 is a schematic view of an electronic signal for
controlling the correction means; and
[0050] FIG. 5 is a diagram of the controlling means for controlling
the correction means of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0051] The apparatus as shown in FIG. 1 comprises a transport
roller 1 with a transport nip 2 in a feed path for feeding a
receiving material 3 originating from a stock (not shown). Roller
system 1 is formed by a drivable roller with a diameter of about 80
mm and a number of soft rubber contact pressure rollers with a
diameter of about 14 mm to provide a slip-free intermittent
transport for the receiving material 3 through the in-line
transport nip 2. The feed path in which the transport nip 2 is
situated is formed by guide plate 4 over which the receiving
material 3 moves. Guide plate 4 is followed in the transport
direction by a carrier plate 5 which forms a carrying surface for a
part of the receiving material 3 which is fed thereon. Printing a
part of the receiving material 3 lying on the carrier plate 5 is
effected by an ink application means such as an inkjet printhead 6.
One or more printheads may be used for applying an ink image to the
receiving material 3 in a known manner.
[0052] As shown in FIG. 1, the carrier plate 5 has a profiled form
consisting of V-shaped ribs 7 which extend parallel to the
direction of advance of the receiving material 3 over the carrier
plate 5. Each rib 7 is formed by a top surface 8, and the top
surface 8 lies in a plane which extends a short distance d beneath
the underside of the printhead 6 (see FIGS. 3A, 3B and 3C). This
distance d is herein referred to as the distance between the ink
application means 6 and the carrier plate 5.
[0053] Between the ribs 7, recesses 9 are formed which serve to
prevent contact between the receiving material 3 on the carrier
plate 5 and the printhead 6 moving in a reciprocating motion 10
over the receiving material 3. The receiving material 3 may locally
curl up, most likely due to moisture absorption during the printing
with an aqueous ink in particular. Any bubbles above the channel
shaped recesses 9 can sag therein.
[0054] The carrier plate 5 is provided with holes 12 which are
connected beneath the carrier plate 5 to an air chamber 13 which is
connected to vacuum means 14 for sucking away air via the holes 12
from the space between the carrier plate 5 and the strip of
receiving material 3 lying on the carrier plate 5. In FIG. 1 the
holes 12 are provided in the top surface 8 of the ribs 7. However,
the holes 12 may also be provided in the channels 9, as depicted in
FIG. 2. Due to the vacuum pressure between the carrier plate 5 and
the receiving material 3, the receiving material 3 is to some
extent pulled in the channels 9 as depicted in FIG. 1. This
situation is schematically depicted in the cross-sectional view of
FIG. 2. Here the depth to which the receiving material 3 sags into
the channels 9 is indicated by the symbol X. This depth normally is
approximately 1 mm, but may be as large as 3-4 mm.
[0055] In order to, at least partially, compensate for the local
variations in the distance between the ink application means 6 and
the receiving material 3, the apparatus according to the present
invention provides a correction means as depicted in the FIGS. 3A,
3B and 3C.
[0056] In a first exemplary embodiment as schematically depicted in
FIG. 3A, the apparatus according to the present invention is
provided with timing means 31 for adjusting the moment of ink
release by the printhead 6 during the motion 10 of the printhead 6
over the receiving material 3 lying on the carrier plate 5.
[0057] In a second exemplary embodiment as schematically depicted
in FIG. 3B, the apparatus of the present invention is provided with
speed adjustment means 41, 43 for adjusting the relative velocity
of the ink application means 6 with respect to the carrier plate 5.
This relative velocity can be adjusted by translation means 41
which moves the carrier plate 5 in a reciprocating motion 42 in a
direction substantially parallel to the direction of the motion 10
of the printhead 6 over the receiving material 3 lying on the
carrier plate 5. In addition or alternatively, the relative
velocity can be adjusted by speed adjustment means 43, which adjust
the velocity of the printhead 6 during its motion 10 over the
receiving material 3.
[0058] In a third exemplary embodiment as schematically depicted in
FIG. 3C, the apparatus according to the present invention is
provided with adjustment means 51, 53 for adjusting the distance d
between the printhead 6 and the carrier plate 5. This distance d
can be adjusted by first movement means 51 for moving the carrier
plate 5 in a direction 52 substantially perpendicular to the motion
10 of the printhead 6 over the receiving material 3 lying on the
carrier plate 5. In addition or alternatively, the distance d can
be adjusted by second movement means 53 for moving the printhead 6
in a direction 54 substantially perpendicular to the motion 10 of
the printhead 6.
[0059] The positions of the channels 9 with respect to the path of
the printhead 6 during its motion 10 over the carrier plate 5 with
said channels 9, and the relative velocity with which the printhead
6 moves over the strip of receiving material 3, are known or can be
determined. The correction means 31, 41, 43, 51, 53 are
controllable by an undulatory electronic signal 60 as depicted in
FIG. 4, wherein the leading edge 61 and tailing edge 62 of the
undulatory signal 60 correspond with downward and upward slopes of
the channels 9 (compare with the channels 9 of FIG. 2).
[0060] The amplitude A of the signal 60 is adjustable depending on
the depth X to which the receiving material 3 sags into the
channels 9. To this end, the above-mentioned exemplary embodiments
of the apparatus according to the present invention can be provided
with controlling means 70 as depicted in FIG. 5. The controlling
means comprises a microprocessor 71 and memory 72. Characteristics
of the print process are stored in the memory means 72. The
particular characteristics of the print process may include: the
receiving material 3, the ink characteristics, the ink image, the
print mode, the carrier plate 5, the distance between the printhead
6 and the carrier plate 5, and the velocity of the printhead 6 with
respect to the carrier plate 5. Coupled to the controlling means 70
is a keyboard control panel 74 for inputting or changing the
characteristics in the memory 72. When, for example, the first
receiving material is replaced by a second receiving material with
different characteristics, the characteristics of the first
receiving material as stored in the memory 72 can be replaced with
the characteristics of the second receiving material.
[0061] The microprocessor 71 can determine or derive the depth X to
which the receiving material 3 will sag into the channels 9 from
the characteristics of the print process as stored in the memory
means 72. In response to this information, the microprocessor 71
produces or adjusts the control signal, for example the amplitude
Amp of the signal 60 as depicted in FIG. 4, which control signal is
sent via an output 75 of the controlling means 70 to an input 35,
45, 46, 55, 56 of the correction means 31, 41, 43, 51, 53,
respectively.
[0062] The invention being thus described, it will be obvious that
the same may be varied in many ways. Such variations are not to be
regarded as a departure from the spirit and scope of the invention,
and all such modifications as would be obvious to one skilled in
the art are intended to be included within the scope of the
following claims.
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